PFK-1 catalysed step is the irreversible step that commits a cell to convert glucose to glycolysis. Apart from the substrate-binding sites, this enzyme contains additional sites (regulatory sites) where allosteric activators or inhibitors bind. ATP not only serves as a substrate for PFK-1 but it also becomes the end product of the glycolytic pathway. When…
Enantiomers are mirror images of each other. These are otherwise called as D and L sugars; for example, D-fructose and L-fructose are enantiomers. If the OH group to the carbon atom lies on the right-hand side, then it is known as D series, as shown in Figure 2.3. Most of the sugars in humans are D-sugars,…
Stereoisomers differing in configuration or arrangement of —OH group on a single asymmetric carbon are known as epimers. For example, mannose and glucose are epimers (Figure 2.2). The position of the —OH group differs only in the C-2 position. Similarly, galactose and glucose are epimers. The position of the —OH group differs only in the…
Carbohydrate metabolism provides the precursors for biosynthetic process and also produces ATP. It is very important for a cell to maintain the concentration of ATP at a nearly constant level. The regulation of glycolysis is carried by an enzyme-linked rate-limiting step. The rate-limiting step for this pathway is an irreversible reaction, and hence, the rate…
The configuration of D-aldoses starting from D-glyceraldehyde is shown in Figure 2.1. This is explained by Kiliani–Fischer synthesis, by increasing the chain length of aldose by one carbon at a time.
Stereoisomers are compounds with the same structural formula but different spatial configuration. A carbon atom is said to be asymmetric if it is attached to four different chemical groups. Monosaccharides contain at least one asymmetric carbon. Isomers are formed due to the presence of asymmetric carbon. The number of isomers in a compound depends on…
During glycolysis, ATP is formed and used in the following reactions (Refer Table 8.1): Table 8.1 Production of High-energy Phosphate in the Catabolism of Glucose The net gain of ATP molecules during glycolysis is eight as seen from the table (10 – 2 = 8). During anaerobic condition, NAD+ is regenerated from NADH by the reduction of…
The major subdivisions of monosaccharides are shown in Table 2.1. Table 2.1 Subdivisions of Monosaccharides Class Aldose Ketose Triose Glyceraldehyde Dihydroxyacetone Tetrose Erythrose Erythrulose Pentose Ribose Ribulose Hexose Glucose Fructose Heptose Sedoheptose Sedoheptulose Monosaccharides are soluble in water and insoluble in organic solvents. They are odourless crystals with a sweet taste. The chemical properties of these…
Glycolysis occurs in all cells, and in some cells, it is the sole source of energy like brain cells, erythrocytes. Organelle: It occurs in cytoplasm of the cells. Steps Glycolysis is also called Embden Meyerhof pathway. In glycolysis, the breakdown of the six-carbon glucose into two molecules of the three-carbon pyruvate occurs in ten steps, Glycolysis…
During glycolysis, ATP is formed and used in the following reactions (Refer Table 8.1): Table 8.1 Production of High-energy Phosphate in the Catabolism of Glucose The net gain of ATP molecules during glycolysis is eight as seen from the table (10 – 2 = 8). During anaerobic condition, NAD+ is regenerated from NADH by the reduction of…